Insect Biocontrol Agents Research Articles

INTEGRATED PEST MANAGEMENT AND ENTOMOPATHOGENIC FUNGAL BIOTECHNOLOGY IN THE LATIN AMERICAS: I-OPPORTUNITIES IN A GLOBALAGRICULTURE

Entomopathogenic fungi (EPF) have been used as insect biocontrol agents separately and in integrated pest management (1PM) worldwide including in the Latin Americas. The proper use of these agents along with other elements and concepts of 1PM has significant impact on the provision of crops. fruits and other agricultura! products Entomopathogenic fungi can play a significant role in the preservation of the natural delicate balance of beneficia! biota and their active spreading from the surrounding natural habitats, such as the tropical rain forest, the humid cloudy forest in the Andes and other important ecosystems, to the agricultura} lands in Central and South America. Of ali known EPF, there are only about half a dozen for which prerequisite aspects of fungal biotechnology for industrial R and D are in place. Because of its precedent setting leadership in the use ofEPF in 1PM and agroecological practices, LatinAmerica stands to gain irnrnensely here and more so if the concept of rational design of bioinsecticides (RADBIO) is employed. The future prospects will depend on a balance of discovery research coupled to a strong and dependable industrialization effort to develop the framework for illustrating public acceptance, commercialization potential and widespread use of EPF in 1PM. The potential for the next generation of mycoinsecticides is now loorning on the horizon.

Light enhances the production of conidia and influences their hydrophobicity in Tolypocladium inflatum

Insect fungal pathogens such as Beauveria bassiana, Metarhizium robertsii, and Tolypocladium inflatum have been used as insect biocontrol agents. Their infection mechanism involves non-specific adhesion to the host cuticle, which is controlled by hydrophobins, small proteins that form an amphipathic monolayer with rodlet morphology on diverse fungal structures. Light is an abiotic factor that may influence a wide range of cellular processes, including conidiogenesis, stress tolerance, and metabolite biosynthesis. Although its effects have been studied in many fungi, little is known about the effects of light on the hydrophobic properties of conidia. The aim of this work was to investigate the influence of visible light on the conidial hydrophobicity of three entomopathogenic fungal species. For this, conidia of B. bassiana, M. robertsii, and T. inflatum were grown either under light or in the dark, drop profiles of water and diiodomethane on conidial surfaces were analyzed, and conidial hydrophobicity was estimated from contact angle measurements. Moreover, conidial production was determined, and their genome was screened with sequences for hydrophobins. Conidia of B. bassiana and M. robertsii are more hydrophobic than conidia of T. inflatum. The light modified the surface tension of T. inflatum; therefore, conidia of T. inflatum became hydrophilic. However, light did not affect the conidial hydrophobicity of B. bassiana and M. robertsii. In addition, light modified the conidial production of B. bassiana and T. inflatum cultures, but it had no effect on the conidial production of M. robertsii. The T. inflatum genome contains two predicted proteins whose sequence is akin to that of proven class II hydrophobins from other ascomycetes. Presumably, these proteins are responsible for the conidial hydrophobicity properties in this fungus. Our study helps elucidate how light affects the conidial hydrophobicity of entomopathogenic fungi.

Utilization of Metarhizium as an insect biocontrol agent and a plant bioinoculant with special reference to Brazil.

Brazil has a long history of using biological control and has the largest program in sugarcane agriculture to which a biocontrol program has been applied. This achievement is at least partly due to the utilization of the entomopathogenic fungus Metarhizium. This well-known fungal genus exhibits pathogenicity against a broad range of arthropod hosts and has been used globally as a biocontrol agent. This fungus is also a root symbiont, and in this capacity, it is a plant growth promoter. However, this feature (i.e., as a plant symbiont) has yet to be fully explored and implemented in Brazil, although the number of reports demonstrating Metarhizium's utility as a plant bioinoculant is increasing. The Brazilian bioproduct industry targets agricultural pests, and is limited to two Metarhizium species represented by four fungal isolates as active ingredients. Entomopathogenic fungi have also been successful in controlling arthropods of public health concern, as shown in their control of mosquitoes, which are vectors of diseases. The isolation of new indigenous Metarhizium isolates from a variety of substrates such as soil, insects, and plants shows the wide genetic diversity within this fungal genus. In this review, we emphasize the significance of Metarhizium spp. for the biological control of insects in Brazil. We also suggest that the experience and success of biological control with fungi in Brazil is an important resource for developing integrated pest management and sustainable strategies for pest control worldwide. Moreover, the future implementation prospects of species of Metarhizium being used as bioinoculants and possible new advances in the utility of this fungus are discussed.

Use of plant viruses as bioherbicides: The first virus-based bioherbicide and future opportunities.

Until recently, only a few plant viruses had been studied for use as biological control agents for weeds, but none was developed into a registered bioherbicide. This position changed in 2015 when the U.S. Environmental Protection Agency (EPA) granted an unrestricted Section 3 registration for tobacco mild green mosaic virus (TMGMV) strain U2 as an herbicide active ingredient (a.i.) for a commercial bioherbicide (SolviNix LC). It is approved for the control of tropical soda apple (TSA, Solanum viarum), an invasive 'noxious weed' in the United States. TSA is a problematic weed in cattle pastures and natural areas in Florida. The TMGMV-U2 product kills TSA consistently, completely, and within a few weeks after its application. It is part of the TSA integrated best management practice (BMP) in Florida along with approved chemical herbicides and a classical biocontrol agent, Gratiana boliviana (Coleoptera: Chrysomelidae). TMGMV is nonpathogenic and nontoxic to humans, animals, and other fauna, environmentally safe, and as effective as chemical herbicides. Unlike the insect biocontrol agent, TMGMV kills and eliminates the weed from fields and helps recycle the dead biomass in the soil. Here the discovery, proof of concept, mode of action, risk analyses, application methods and tools, field testing, and development of the virus as the commercial product are reviewed. Also reviewed here are the data and scientific justifications advanced to answer the concerns raised about the use of the virus as a herbicide. The prospects for discovery and development of other plant-virus-based bioherbicides are discussed. This article is protected by copyright. All rights reserved.

Insecticidal Potentials and Identification of Bioactive Compounds from Extracts of Bacopa Floribunda and Ludwigia Decurrens Plants

The negative impact of insecticides used to combat insect-borne plant ailments cannot be emphasized, as they have had a major influence on plant yields throughout time, and the side effect of insecticide residue on consumers cannot be overstated either. Callosobrochus maculatus is an insect that attacks cowpeas and has the potential to significantly reduce crop productivity. This research developed from investigations into the utilization of biological control technologies that have little or no harmful influence on humans or the environment. The leaves of Bacopa Floribunda (BFL) and Ludwigia Decurrens (LDL) were air dried, powdered, and extracted with n-hexane. The insecticidal activities were carried out according to protocol, and the LC50 was determined using online software from AAT Bioquest, Inc. The presence of bioactive compounds was detected using GC-MS. The Callosobrochus maculatus mortality rate was found to be a function of exposure time and concentration of the extracts, with the maximum mortality rate (66.67±8.82 percent) occurring after 72 hours at 0.5 mg/ml for BFL extract. The highest mortality rate (70.00 ±5.77 percent) was obtained for the LDL extract at 72 hours at 0.5 mg/ml of the extract concentration, which was better than the other extract (BFL) at 0.5 mg/ml. The lethal concentration LC50 for BFL varies from 0.251 (24 hours), 0.276 (48 hours), and 0.223 (72 hours), while the LC50 for LDL extract is 0.228 (24 hours), 0.039 (48 hours), and 0.663 (72 hours) (72 hrs). The presence of chemicals found could be linked to the extracts’ insecticidal properties. The excellent potential of the extracts as insect biocontrol agents against Callosobrochus maculatus can be recommended for future research as insect biocontrol agents.

Biological Control of Three Eupatorieae Weeds in South Africa: 2011–2020

Several weed species within the asteraceous tribe Eupatorieae, all with a neotropical origin, are invasive in South Africa. Three of these form the subject of this review paper: Chromolaena odorata (triffid weed), Campuloclinium macrocephalum (pompom weed), and Ageratina adenophora (crofton weed). The three species invade different habitats and regions, and all have biological control (biocontrol) agents established on them. Ageratina adenophora was the first of these weeds to be subjected to a biocontrol programme in South Africa, with two agents (an insect and a pathogen) released and established in the 1980s. Two biocontrol agents were established on C. odorata in the early 2000s, and a third one, first released in 2011, has persisted for at least eight years – all three are insects. One insect biocontrol agent was established on C. macrocephalum in 2013, although a pathogen had appeared on the weed several years earlier. Chromolaena odorata and A. adenophora are under substantial control in certain habitats, but negligible in others. The biocontrol agent on C. macrocephalum released in 2013 is causing significant damage to the plant where it has established well. Several other biocontrol agents have been released on C. odorata but have failed to establish. For all three weedy Eupatorieae, it is considered desirable to establish additional biocontrol agents, so as to increase the level of control of these priority targets in South Africa. An additional biocontrol agent has already been approved for release against C. macrocephalum, while one is close to being approved for C. odorata. There are several possibilities for additional biocontrol agents for A. adenophora.

Predation functional response and demographic parameters of Orius albidipennis (Hemiptera: Anthocoridae) on Schizaphis graminum (Hemiptera: Aphididae): effect of host plant morphological attributes

ABSTRACT Plant morphological attributes diversely affect the biocontrol agents of phytophagous insects. In the current study, the effect of physical plant features on life table characteristics and functional response of Orius albidipennis (Rueter) females feeding on Schizaphis graminum (Rondani) was investigated on two common wheat cultivars (Falat and Pishtaz) differing in leaf morphological features. The trichome density considerably influenced a broad spectrum of attributes related to the performance of O. albidipennis. Although Orius predators exhibited type III of functional response on both cultivars, they had lesser searching efficiency and higher handling time on Pishtaz than on Falat cultivar. The maximum attack rate was greater on Falat than on Pishtaz. Lesser maximum predation and greater handling time of the Orius predators on Pishtaz might be imputed to the significantly more condensed surface trichomes of its leaves than that of Falat leaves, which physically prevented movement of the bugs and decreased prey encounter rate. Moreover, an increase in trichome density negatively influenced the foraging behaviour of the predatory bug. Females were also found to prefer leaves with fewer trichomes as oviposition hosts. It seems that trichomes provided hindrance to the Orius bug. The intrinsic rate of increase (rm) was significantly greater on Falat than on Pishtaz cultivar. Similarly, the net reproductive rate and finite rate of increase were greater on Falat than on Pishtaz. To recapitulate, it could be stated that the efficiency of O. albidipennis in controlling S. graminum on wheat may be more beneficial in cultivars with lower trichome density.

Genomic analysis of the nomenclatural type strain of the nematode-associated entomopathogenic bacterium Providencia vermicola

BackgroundEnterobacteria of the genus Providencia are mainly known as opportunistic human pathogens but have been isolated from highly diverse natural environments. The species Providencia vermicola comprises insect pathogenic bacteria carried by entomoparasitic nematodes and is investigated as a possible insect biocontrol agent. The recent publication of several genome sequences from bacteria assigned to this species has given rise to inconsistent preliminary results.ResultsThe genome of the nematode-derived P. vermicola type strain DSM_17385 has been assembled into a 4.2 Mb sequence comprising 5 scaffolds and 13 contigs. A total of 3969 protein-encoding genes were identified. Multilocus sequence typing with different marker sets revealed that none of the previously published presumed P. vermicola genomes represents this taxonomic species. Comparative genomic analysis has confirmed a close phylogenetic relationship of P. vermicola to the P. rettgeri species complex. P. vermicola DSM_17385 carries a type III secretion system (T3SS-1) with probable function in host cell invasion or intracellular survival. Potentially antibiotic resistance-associated genes comprising numerous efflux pumps and point-mutated house-keeping genes, have been identified across the P. vermicola genome. A single small (3.7 kb) plasmid identified, pPVER1, structurally belongs to the qnrD-type family of fluoroquinolone resistance conferring plasmids that is prominent in Providencia and Proteus bacteria, but lacks the qnrD resistance gene.ConclusionsThe sequence reported represents the first well-supported published genome for the taxonomic species P. vermicola to be used as reference in further comparative genomics studies on Providencia bacteria. Due to a striking difference in the type of injectisome encoded by the respective genomes, P. vermicola might operate a fundamentally different mechanism of entomopathogenicity when compared to insect-pathogenic Providencia sneebia or Providencia burhodogranariea. The complete absence of antibiotic resistance gene carrying plasmids or mobile genetic elements as those causing multi drug resistance phenomena in clinical Providencia strains, is consistent with the invertebrate pathogen P. vermicola being in its natural environment efficiently excluded from the propagation routes of multidrug resistance (MDR) carrying genetic elements operating between human pathogens. Susceptibility to MDR plasmid acquisition will likely become a major criterion in the evaluation of P. vermicola for potential applications in biological pest control.

Insecticidal impacts of Bacillus flexus S13 biofilm'extracellular matrix' on cowpea weevil, Callosobruchus maculatus

Abstract In an attempt to throw light on the chemical composition of the extracellular matrix (ECM) of Bacillus flexes S13; biofilm’ and its potential activity as insect biocontrol agents. This study investigated the insecticidal efficacy of ECM of Bacillus flexus; S13 against adults of Callosobruchus maculatus. The toxicity results revealed LC50 values as 22.6455 g/100 ml and 10.8524 g/100 ml after 24 and 48 h respectively. Also, the Biochemical assays revealed a significant reduction in total protein, total lipids and chitin contents in survival adults treated with LC50 of Bacillus flexus' ECM where's, the total protein was decreased down to the half (15.54 mg/g) in adults treating with ECM compared to untreated-negative control (39.34 mg/g) while the positive control group treated with NaCl showed a mild decrease (23.57 mg/g). Furthermore, the GC/MS analyses of the methanolic solution of Bacillus flexus ECM showed a high content of polyphenols especially; flavonoid compounds while the major compound was (3, 5, 7, 3\, 4\, penta hydroxyl flavone)with percentage of (40.93%).

Wasps (Insecta: Hymenoptera) associated to trees in urban parks of Bogota’s city, Colombia

Urban trees are a source of food resources, habitat and refuge for the biodiversity that occurs in cities. However, the taxonomic identity and status of each plant species as native and / or exotic of in an ecosystem influences its interactions with biodiversity. Wasps are one of the main insects present in terrestrial ecosystems, including urban ecosystems, as components of their biodiversity, playing an important role as biocontrol agents (predators and parasitoids) of populations of other insects associated with urban flora or as phytophagous. Seeking to deepen into the knowledge of the diversity of wasps in the city of Bogotá and their ecological interactions, in this study the diversity of wasps associated with three native and three exotic species frequently in urban parks of the city was evaluated. In total, 22 wasp families and 227 morphospecies were identified. The families Bethylidae, Chalcididae and Crabronidae are recorded for the first time in Bogotá. On the other part, the families Eulophidae, Ichneumonidae and Braconidae were the ones that contributed with the most richness and abundance in this study. Regarding their association with the evaluated plant species, a greater diversity of morphospecies associated with native tree species was found, however, there is an effect of the taxonomic identity and the factor park on the results that are discussed. It highlighting the importance of conserving the native urban flora in green spaces of Bogota’s city, in order to maintain and preserve the diversity of wasps principally with parasitoid and predator habits and thus enhance their role as natural biocontrol agents of insects that affect the health of urban trees, at the same time that ecological processes and functionality of this urban ecosystem would be stimulated.

Field application of allelopathic bacteria to control invasion of little seed canary grass in wheat.

Development of successful biological weed control can help to resolve various environmental challenges created by the chemical and mechanical weed control. The current study is aimed at investigating the potential of allelopathic bacteria (hereinafter as AB) for biological weed control in wheat rather than the traditional areas of plant allelopathy, phyto-pathology, and insect biocontrol agents. Eleven strains of AB were obtained that were inhibitory to little seed canary grass of which 5 also inhibited wheat in our previous studies. The remaining strains indicated the potential for biological control of this weed in wheat. Five efficient strains were selected for this purpose to conduct pot and field trials. Seeds of little seed canary grass were sown together in potted soils with wheat seeds inoculated with AB strains. A subsequent field trial was conducted at a site selected based on chronic infestations of canary grass. Seeds of the weed and inoculated wheat were co-seeded directly in field soil. For inoculation, these strains were formulated in sterilized peat and applied to seeds. In pot trials, the invasion of little seed canary grass in wheat reduced wheat grain yield up to 59.9%. Four strains suppressed the weed which resulted in recovery wheat grain yield losses from 20.1 to 66.9%. The field trial showed that the invasion of little seed canary grass reduced wheat grain yields up to 53.9%. Four strains suppressed the weed which resulted into recovery of grain wheat grain yield losses 34.3 to 64.3%. These findings were consistent with improvement of other agronomic, physiological, and chemical parameters of the crop where the four strains of AB (L9, T42, 7O0, and O010) were applied.

Unveiling of Swainsonine Biosynthesis via a Multibranched Pathway in Fungi.

The indolizidine alkaloid swainsonine (SW) is a deadly mycotoxin to livestock that can be produced by different plant-associated fungi, including the endophytic entomopathogenic fungi Metarhizium species. The SW biosynthetic gene cluster has been identified but the genetic mechanism of SW biosynthesis remains obscure. To unveil the SW biosynthetic pathway, we performed gene deletions in M. robertsii, heterologous expression of a core biosynthetic gene, substrate feedings, mass spectrometry, and bioassay analyses in this study. It was unveiled that SW is produced via a multibranched pathway by the hybrid nonribosomal peptide-polyketide synthase (NRPS-PKS) gene cluster in M. robertsii. The precursor pipecolic acid can be converted from lysine by both the SW biosynthetic cluster and the unclustered genes such as lysine cyclodeaminase. The hybrid NRPS-PKS enzyme produces three intermediates with and without domain skipping. Intriguingly, the biosynthetic process is coupled with the cis to trans nonenzymatic epimerization of C1-OH for both hydroxyl- and dihydroxyl-indolizidine intermediates. We also found that SW production was dispensable for fungal colonization of plants and infection of insect hosts. Functional characterization of the SW biosynthetic genes in this study may benefit the safe use of Metarhizium fungi as insect biocontrol agents and the management of livestock pastures from SW contamination by genetic manipulation of the toxin-producing fungi.

Surrounding landscape influences the abundance of insect predators in rice field

BackgroundNatural enemy abundance in a crop plot depends on its prey presence and also influenced by habitats close to field. Landscape changes are also important factors driving pest and natural enemy population abundance in a specific crop field. Examining these kinds of effects on insect pests or biocontrol agents, as well as analysis of their functional food webs, would be asset to make a fruitful pest management programme at local scales. Therefore, this study was undertaken to evaluate the impact of surrounding landscape on the abundance insect predators in rice field.ResultsThis study revealed a dependency on rice bund margin width, with spider populations increasing with increased bund widths. Conversely, population abundance did not rely on the number of weed species observed on earthen ridge around the rice field. In general, relative abundances of predator populations differed significantly across the three landscapes tested. Among the four predators of rice insect pest, the green mirid bug showed highest number irrespective of landscape. Comparatively, higher predator diversity (Shanon diversity) was observed in landscape I followed by landscape III and landscape II. All landscapes showed different diversity indices indicating heterozygosity existed in each study site. These landscape diversity influences the predator’s abundances at a local scale. Variogram derived from this study also indicated the landscape heterozygosity existed in studied locations which can also explain the predator’s abundances in rice field at locale scale.ConclusionThese findings suggest that predators of rice insect pests are landscape specific. Therefore, characterization of each local landscape in Bangladesh rice production landscapes are necessary before planning and implementation of integrated pest management. Geospatial analysis of local landscape would be more effective to analyze such unique characteristics. As a step in this direction, preliminary variography analyses using the RED spectral band of December 2016 LANDSAT 8 imagery propose an initial learning suite of methods for describing useful local characteristics affecting rice pest predators.

Efficacy of chitosan/double-stranded RNA polyplex nanoparticles for gene silencing under variable environmental conditions

Chitosan/dsRNA polyplex nanoparticles have shown great potential as insect biocontrol agents. Here, we show that polyplex nanoparticles have their gene silencing capacity altered by environmental variables.

Molecular Regulators of Entomopathogenic Nematode-Bacterial Symbiosis.

Entomopathogenic nematodes are parasitic organisms with an exceptional capacity to infect rapidly and efficiently a wide range of insect species. Their distinct pathogenic properties have established entomopathogenic nematodes as supreme biocontrol agents of insects as well as excellent models to simulate and dissect the molecular and physiological bases of conserved strategies employed by parasitic nematodes that cause infectious diseases in humans. The extreme infectivity of entomopathogenic nematodes is due in part to the presence of certain species of Gram-negative bacteria that live in mutualistic symbiosis during the infective juvenile stage, which forms the central part of the nematode life cycle. Both nematodes and their mutualistic bacteria are capable of interfering and undermining several aspects of the insect host innate immune system during the infection process. The mutualistic bacteria are also able to modulate other biological functions in their nematode host including growth, development, and reproduction. In this review, we will focus our attention on the mutualistic relationship between entomopathogenic nematodes and their associated bacteria to discuss the nature and distinct characteristics of the regulatory mechanisms, and their molecular as well as physiological components that control this specific biological partnership.

Laboratory tests to estimate the non-target impacts of four Aphidius spp. parasitoids in the field

A ‘risk score’ approach to help determine the potential impact of biological control agents on non-target species, previously proposed for weed biocontrol agents, was examined in an ex post study for insect biocontrol agents. ‘Risk scores’ (% parasitism for non-target aphid species/% parasitism for target aphid species) were calculated for 19 aphid (New Zealand adventive and indigenous) species and 4 introduced (New Zealand) Aphidius biocontrol species, based on previously published choice and no-choice host range laboratory testing. Field hosts for each Aphidius parasitoid and aphid host combination were also examined through an extensive literature review. Strong correlations between ‘risk scores’ for both choice and no-choice laboratory assays and field host binary values (host: yes or no) were obtained for each Aphidius/aphid dataset, but there was no threshold score that indicated using the approach to predict parasitoid field host ranges could result in type II errors. In contrast, a second analysis that categorized aphid hosts as ‘major field hosts’, if literature records indicated high (≥15%) levels of parasitism in the field, showed a clear threshold risk score predicting whether an aphid was a major field host in no-choice tests. We conclude that this approach could potentially be used to predict the likelihood of the impact of Aphidius biocontrol agents on non-target aphid species. We discuss the pros and cons of this approach to help scientists and regulators in the assessment for new biocontrol agent introductions, including the need for this ‘risk score’ approach to be tested on a greater range of insects.

Impacts of the agricultural transformation of the Canadian Prairies on grassland arthropods

AbstractThe prairie grasslands have been transformed to become the primary source of agricultural production in Canada. Soon after its establishment, the Biological Survey of Canada recognised the urgent need to document the arthropods of the prairie grasslands, especially in the few pristine remnants. Although this initiative has yielded considerable progress in documenting the species present in the Prairies Ecozone, comprehensive ecological studies are sparse. Landscape effects on arthropods are well studied elsewhere, but no equivalent studies have been published for the Canadian Prairies. Crop rotation varies landscape composition annually, changes host plant resources in fields, and interacts with other agricultural inputs to disturb pest and beneficial arthropods. Despite only a handful of studies on grazing, there is an emerging pattern: moderate grazing increases arthropod diversity and benefits certain arthropod guilds. Abiotic inputs elicit variable responses from different arthropod taxa; Carabidae (Coleoptera) are best studied, with some information available for ants (Hymenoptera: Formicidae) and aquatic arthropods. Biotic inputs include arthropods released for biocontrol of weed and insect pests; evidence indicates that biocontrol agents of insects have a greater potential for impact on native communities of arthropods. The studies reviewed here reveal important trends and research gaps to be addressed in the future.

The Attributes of Survival in the Formulation of Entomopathogenic Nematodes Utilised as Insect Biocontrol Agents

Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis and their associated symbiotic bacteria of the genera Xenorhabdus and Photorhabdus, are efficient biological control agents, due to their ease of culture, their high fatality against key insect pests and their safety in use. However, their commercial utilisation is limited by their finite shelf life, both in storage and in formulations. Thus, efficient storage in the formulation of EPNs is essential so as to attain success in integrated insect pest management strategies. This paper reviews the latest information that is available on EPN storage, formulation, quality and application methods, coupled with improvement strategies for the effective control of insects. Nematode survival mechanisms investigated were heat and cold tolerance, desiccation, osmotic stress, hypoxia and energy reserves, among others, in storage, field or formulations. Their influence on the formulation of EPNs is also discussed.

Laboratory Bioassays to Determine Susceptibility of Woolly Apple Aphid,Eriosoma lanigerum(Hausmann) (Hemiptera: Aphididae), to Entomopathogenic Nematodes

Woolly apple aphid (WAA), Eriosoma lanigerum, is an important pest of apples, occurring throughout the apple-growing regions of the world. Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have generated intensive interest as inundative biocontrol agents of pest insects. Considering resistance of WAA against certain insecticides and the inability of parasitoids to control the aphid successfully early in the season, EPNs offer an alternative biocontrol option. The susceptibility of WAA to seven indigenous EPN species was tested in laboratory bioassays in which Steinernema yirgalemense and Heterorhabditis zealandica were identified as being the most effective against the subterranean adult females of the WAA, with infection rates of 39%and 28 %, respectively. The effect of E. lanigerum size showed that the last instar is most susceptible to infection, whereas none of the crawlers were infected. Increasing the exposure time of the aphids and nematode concentration had no positive effect on the WAA infection rate. On evaluating the ability of infective juveniles of S. yirgalemense and H. zealandica to tolerate exposure to imidacloprid, both nematode species were found to be compatible at the recommended dosage, with no significant nematode mortality having occurred. Neither did imidacloprid affect the ability of the nematodes to infect their hosts after 24 h exposure. The associated bacteria, isolated from 12 EPN isolates, showed a visual inhibitory growth effect, when they were exposed to the haemolymph of WAA. From these results, it is concluded that, although S. yirgalemense showed some infection of WAA, its low mortality and inability to complete its life cycle within the host, limits its effectiveness as a biological control agent against the subterranean stages of WAA in apple orchards.

Complete genome sequence of Bacillus thuringiensis Bt185, a potential soil insect biocontrol agent

Bacillus thuringiensis Bt185 and its insecticidal spectrum-expanded engineering strains are considered as potential biocontrol agents to soil insect Holotrichia parallela, Holotrichia oblita or Anomala corpulenta. Here we reported the complete genome of strain Bt185, it harbors eight plasmids, and plasmid pBT1850294 carries three cry8 genes.